Wireless communication systems have evolved greatly over the past few years. Current wireless communication systems are capable of transmitting and receiving broadband content such as streaming video and audio. Wireless communication systems generally are comprised of wireless devices and access points, referred to as “base stations”, which provide communication services to the wireless devices. The area covered by a single access point, or base station, is commonly called a “cell”. Wireless devices roam into different cells as they move around and connect to different base stations. Typically, the base stations regularly transmit broadcast messages which provide information about the particular base station, as well as the network, its structure, and its capabilities. These broadcast messages are used by wireless devices to obtain information about the network and further obtain the appropriate parameters for communication with the base stations. In most wireless communication standards and technologies, the broadcast messages are fairly large and are not continuously transmitted by the network. The broadcast messages, are instead, transmitted according to some time schedule that each base station defines in order to reduce overhead and use of wireless resources.
Wireless devices typically operate on a battery, which has a limited lifetime. Conserving battery resources at the mobile device is essential in order to prolong the time a mobile device can operate without requiring its battery to be recharged. A common method of extending battery life in modern wireless communication systems is by introducing an additional mode of operation for mobile devices, typically called “idle mode”. During normal operation, the wireless communication network tracks the movements of each active mobile device down to the base station level, i.e., it is constantly aware of which base station each mobile device is connected to at any given time. When a mobile device is not actively engaged in some sort of communication with the network, this level of granularity is no longer needed and the network can elect to track the mobile device at a much coarser level. The mobile device can, in turn, switch off its radio receiver and transmitter and thus conserve battery resources. This is done by allowing the mobile device to enter idle mode. Typically in idle mode, the location of a device is tracked by the network at the level of group of base stations, typically called a “paging group”.
An idling mobile device can switch off its radio and other functions and is not required to monitor every transmission by the network. However, an idling wireless device is still required to periodically wake up and monitor the network's transmissions for a short time, typically called the “paging listening interval”. This is done so that the network can inform the mobile device of any incoming traffic. When the wireless device is in a sleep mode, we typically say that it is in a “sleeping time interval”. The schedule and relative duration of sleeping to paging listening intervals can be different for each wireless device, but typically remains unchanged as long as the wireless device stays within the same paging group.
A wireless device, when it enters idle mode, is given a particular sleeping and paging interval schedule by the base station. A listening/paging interval schedule is typically defined through a set of parameters that are communicated to each idling wireless device. These parameters typically consist of a paging frequency and a paging offset, which jointly define how often the wireless device is expected to become available for paging and traffic notifications from the network. Typically, a number of schedules, for different levels of availability, are configured in each paging group and the wireless device is given one of the available schedules when it enters idle mode. The wireless device is also typically responsible for monitoring if it has moved into the area of a different base station, but is only required to notify the network when it roams into the area of a different paging group.
In modern wireless communication systems, the base station is typically responsible for regulating wireless transmissions within its area (within its cell). This is typically done by enforcing some slotted time structure in which the schedule for transmissions and receptions for the next unit of time is periodically communicated by a base station to all the wireless devices in its cell. The time unit used for regulating transmissions in a cell is commonly referred to as a “frame”. At the beginning of each frame a base station transmits a minimal amount of identifying information to make each wireless device aware of the origin of the communicated schedule. This information is kept at a minimum due to the increased frequency of transmissions. For example, typical frame sizes are in the order of 5 msec or even 1 msec. Transmitting a large amount of information at the beginning of each frame unnecessarily increases overhead and wastes system resources. Information, such as the paging group to which a base station belongs and other details about the structure of the upstream and downstream channels and the settings currently in use, are reserved for larger system broadcast transmissions which happen much less frequently.
Typically, when an idling wireless device roams into the area of a base station belonging to a different paging group, it has to wait for the system broadcast transmissions, DCD/UCD in order to detect if it has roamed into a different paging group, and determine the appropriate actions (e.g., a wireless device is required to notify the network when it roams into a different paging group). Generally, the wireless device has no information about the time schedule of the DCD/UCD transmissions. Therefore, the wireless device has to monitor every subsequent frame from the new base station until the system broadcast information appears, which unnecessarily expends battery life of the wireless device.
Therefore a need exists to overcome the problems with the prior art as discussed above.